Hightech Equipment to Drill through Brittle Rock Formations and Soft Rock.

The Single Shield TBM belongs to a category of machines which are fitted with an open shield. Tunnelling machines described as open shields are machines without a closed system for pressure compensation at the tunnel face. In other words, no excavation chamber has been defined.TBMs fitted with a shield are used on brittle rock formations or soft rock. They have a very wide range of applications on hard rock.

Protected by the shield (1), a cylindrical tapered steel structure, the machine extends and drives forward the tunnel practically automatically. In order to drive the tunnel forwards, the Single Shield TBM is supported by means of hydraulic thrust cylinders (2) on the last segment ring (3) installed. The cutting wheel (4) is fitted with hard rock disks, which roll across the tunnel face, cutting notches in it. These notches dislodge largish chips of rock. Muck bucket lips (5), which are positioned at some distance behind the disks, carry the extracted rock behind the cutting wheel. The excavated material is brought to the surface by conveyers (6).

The required driving torque of the cutterhead for Single Shield TBMs can be calculated more accurately than that of any full face tunnelling machine. In addition to a many other parameters, the torque depends largely on the degree of penetration of the disks and their contact pressure.

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